Hi,
I don't know about Imuran, but yes there are withdrawal symptoms from prednisone. Always follow your doctors instructions for tapering the pred, so that your adrenal glands wake up. Symptoms can be weak, lethargic, lightheaded, no appetite, generally feeing like you have a bad flu where you can't get your head up off the pillow. One can ck out adrenal suppression for more info..
Take care,
Julia